bcachefs: add eytzinger0_find_ge self test

bcachefs: add eytzinger0_find_ge self test

Add an eytzinger0_find_ge() self test similar to eytzinger0_find_gt().

Note that this test requires eytzinger0_find_ge() to return the first
matching element in the array in case of duplicates.  To prevent
bisection errors, we only add this test after strenghening the original
implementation (see the previous commit).

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>